Outdoor (neg temp) sensor for battery power project

[maddhin]

Hi,

I have successfully built temp sensors based on "my slim node" here in the forum (2xAA battery, ATMega328P, NRF24l01). I love these little things!

But now I would like to build a sensor for outdoors to measure the outside temperature. And fail. All of the usual suspects like HTU21D cannot measure temperatures below 0. Then there is the Dallas D18B20, which can do below 0 but needs 3+V to operate.

How would you solve this? Go with the D18B20 and use a booster? Or is there another sensor I missed?

Any input is much appreciated!

[electrik]

Have a look at the bme280. Low power and low voltage and starts at -40 °C
https://www.bosch-sensortec.com/products/environmental-sensors/humidity-sensors-bme280/

It is available on Aliexpress also

[mfalkvidd]

If you haven't already, see https://forum.mysensors.org/topic/3801/witch-temp-hum-sensor-is-best-to-use-for-battery-powered-sensors

[A3V]

You can also use an analog temperature sensor like MCP9700.
Needs calibration and small calculations to get the results. There are libs available but you can do it in your code as well.
Is low power, low voltage, and can do negative.
I use it in an outdoor sensor on a similar slim node sending every 20 min. Running about 1 year now on 2 AA's.

[NeverDie]

In addition to what has already been said, you'll also want to switch to Energizer lithium ion primary batteries--or some other form of power--because Alkaline batteries don't work well below freezing. You can confirm this for yourself by reviewing alkaline battery spec sheets.

[dhaillant]

Hey, I have a fully working node (2xAA battery, ATMega328P, NRF24l01 and the classic DS18B20) in my freezer (around -25°C)...